Release 3rd December 2025

Overview

This release adds NotFoundException to distinguish not found from cannot be found conditions. and extends the functionality of @AlternateIndex to support multiple alternate indexes on segments and aspects that are referenced by multiple entities.

Not Found

Prior to this release Get(...) calls did not distinguish between Not Found and not found because of IO error. To improve the handling of missing values several changes have been made:

Additional Exception class NotFoundException
KeyRef<> (reference to another element) changed to return null when a value cannot be found
RefSingle<> (reference to an aspect) changed to return null when a value cannot be found

AlternateIndex

Alternate indexes are created automatically whenever there is a path from an element from another element, but can be added to support access from a view. The prime example is Edge which is defined (in the Hilang prelude) as

"edge between nodes"
view Edge 
( /* keys */
    From        : Node,
    To          : Node,
    TypeName    : String
)
{ /* values */
    Name        : String
};

@AlternateIndex enables an element to index the key/value that corresponds to the From key member for indexed access from a Node.Froms extension property

For the model

entity CostCentre (Id : Int32) [Costs : Cost (CostCentre = this)];
aspect Cost {CostCentre : CostCentre, Amount : Decimal};

with

entity Asset (...) {...} [Cost : Cost];
entity Project (...) {...} [Cost : Cost];

Concreate elements AssetCost and ProjectCost will be created indexes AssetCostCostCentre.Index and ProjectCostCostCentre.Index

Source edit will change the source to

entity CostCentre (Id : Int32) [Costs : Cost (CostCentre = this)];
aspect Cost 
{
  @AlternateIndex("AssetCost", 42)
  ,AlternateIndex("ProjectCost", 43) 
  CostCentre : CostCentre, Amount : Decimal};

To ensure the index Id is not used for something else resultuing in an incompatible model and store.

how does CostCentre know what (Asset/Project/ etc) the Cost is for? The aspect Cost is transformed to a view that is equvilent to

view Cost (owner : Any) {CostCentre : CostCentre, Amount : Decimal};

the (C#) hiperspace query

from centre in space.CostCentres 
select centre.Id, (from line in centre.Costs 
                   let asset = line.owner.Is<Asset>() ? Amount : 0 
                   let project = line.owner.Is<Project>() ? Amount : 0 
                   group line by line.CostCentre into totals
                   select new { Projects = totals.Sum(v => v.asset),
                                Assets = totals.Sum(v => v.project)})

Will return the total costs by type for each CostCentre

Inherited Index

This model defines an overall trade type with three different implementations for {FI, EQ, FX} that have different properties for the different asset-classes. Trade is referenced by Book, the extension property Book.Trades returns a collection of Trade has a Book equal to the current Book. For efficient access, and index is created for the Trade.Book that is inherited by each implementation.

The syntax Banking.FI.Trade : Banking.Trade = Banking.Trade() means Banking.FI.Trade:

Inherits keys / values / extensions / properties from Banking.Trade (via :)
Can be viewed as a Banking.Trade (via =)

view Banking.Trade (Id : String) 
{Book : Banking.Book};
entity Banking.FI.Trade : Banking.Trade = Banking.Trade();
entity Banking.FX.Trade : Banking.Trade = Banking.Trade();
entity Banking.EQ.Trade : Banking.Trade = Banking.Trade();
entity Banking.Book (Id : String) [Trades : Banking.Trade (Book = this)];

Adding %ids to the model, with result in a source edit to a # id to each element, key/value and extension property, and @AlternateIndex property for each generated concrete index.

view Banking.Trade #45 (Id : String) 
{@AlternateIndex("Banking.EQ.Trade", 52) 
 ,AlternateIndex("Banking.FI.Trade", 48)
 ,AlternateIndex("Banking.FX.Trade", 50) 
 Book : Banking.Book};
entity Banking.FI.Trade : Banking.Trade = Banking.Trade() #49;
entity Banking.FX.Trade : Banking.Trade = Banking.Trade() #51;
entity Banking.EQ.Trade : Banking.Trade = Banking.Trade() #53;
entity Banking.Book #47 (Id : String #1) [Trades : Banking.Trade (Book = this) #54];

subsequent compilation of the model will result in the indexes using the same Id value when stored.
NB the #id can be of any value, but can never to reused for a different purpose once used with a Hiperspace.

Source Editing

When the directive %ids is added to a hilang model, the source code is edited to add #id values to ensure that the schema can be evolved without the risk of introducing incompatible changes.

know issue: Source editing lacks the context of other edits to a line of hilang source @AlternateIndex("Banking.EQ.Trade", 52) @AlternateIndex("Banking.FI.Trade", 48) Book : Banking.Book will create a syntax error the next time the schema is compiled because @ is the prefix for a comma-separated list of one-or-more attributes. The code needs to be edited to change subsequent @ to ,

NuGet

Release 3rd December 2025 Release 24th November 2025 Release 15th November 2025